High voltage startup booster

ABSTRACT

An electronic device includes a circuit board that manages supply of electricity to the electronic device. The circuit board includes an integrated circuit and an external capacitor coupled to a supply terminal of the circuit board. During a startup operation of the integrated circuit, the integrated circuit supplies a first charging current to charge the capacitor to a supply voltage value. The circuit board includes a boost circuit that receives a portion of the first charging current and outputs a second charging current that augments charging of the capacitor. The second charging current is an amplification of the first charging current. The integrated circuit enables operation of the electronic device after the capacitor is charged to the supply voltage value.

BACKGROUND Technical Field

The present disclosure relates to the field of circuits for controllingthe supply of power to electronic devices.

Description of the Related Art

Many electronic devices are powered by high voltages. These electronicdevices often include circuit boards that manage the supply of power tothe electronic device. When a voltage is first received from a voltagesource, an integrated circuit enters a startup mode in which theintegrated circuit charges one or more external components. The speed ofthe startup mode is limited by the current that the integrated circuitcan supply during startup. The size of the current is limited by howmuch heat the integrated circuit can safely dissipate.

BRIEF SUMMARY

In one embodiment, a device includes an input terminal that receives aninput voltage, an output terminal that supplies an output voltage, and afirst capacitor. The device includes an integrated circuit that controlssupply of the output voltage to the output terminal. The integratedcircuit includes a supply voltage terminal that receives a supplyvoltage and is coupled to the first capacitor. The integrated circuitincludes a high voltage startup circuit that begins charging the firstcapacitor to the supply voltage value by supplying a first chargingcurrent from the supply voltage terminal when the input terminalreceives the input voltage. The device includes a boost circuit thataugments the charging of the first capacitor by generating a secondcharging current based on the first charging current.

In one embodiment, a method includes charging, to a supply voltagevalue, a first capacitor coupled to a supply voltage terminal of anintegrated circuit by supplying a first charging current from theintegrated circuit as a startup procedure of the integrated circuit. Themethod includes augmenting the charging of the first capacitor to thesupply voltage level by generating, with a boost circuit external to theintegrated circuit, a second charging current by amplifying a portion ofthe first charging current. The method includes enabling, with theintegrated circuit, supply of an output voltage to an electronic deviceresponsive to the first capacitor reaching the supply voltage level.

In one embodiment, the method includes receiving an input voltage at aninput terminal of a circuit board and outputting, responsive toreceiving the input voltage, a first charging current from an integratedcircuit positioned on the circuit board. The method includes passing atleast a portion of the first charging current through a base terminal ofa bipolar transistor positioned on the circuit board. The methodincludes charging a first capacitor to a supply voltage value of theintegrated circuit by supplying a second charging current from thebipolar transistor and enabling, with the integrated circuit, supply ofan output voltage from the circuit board responsive to the firstcapacitor reaching the supply voltage value.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram of an electronic system, according to oneembodiment.

FIG. 2 is a schematic diagram of a circuit board, according to oneembodiment.

FIG. 3 is a schematic diagram of a circuit board during a startupoperation, according to one embodiment.

FIG. 4 illustrates a plurality of graphs of electronic signals,according to one embodiment.

FIG. 5 is a flow diagram of a process for managing supply of electricityto an electronic device, according to one embodiment.

FIG. 6 is a flow diagram of a process for managing supply of electricityto an electronic device, according to one embodiment.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of an electronic system 100, according to oneembodiment. The electronic system 100 includes a voltage source 102, andan electronic device 104. The electronic device 104 includes a circuitboard 106. The electronic system 100 can include other componentswithout departing from the scope of the present disclosure.

The voltage source 102 provides electricity for powering the electronicdevice 104. The voltage source 102 can include a municipal power gridthat provides electricity to a municipality for powering electronicdevices and circuits. The voltage source 102 can include an auxiliarypower supply for providing auxiliary power in the event of a fault in amunicipal power grid. The voltage source 102 can include batteries,flywheels, super capacitors, combustion powered generators, windturbines, hydroelectric generators, or other sources of electricity.

In one embodiment, the voltage source 102 supplies an AC voltage. In theexample of a municipal power grid, the voltage source 102 may supply ACvoltages including 90 V, 115 V, 230 V, 300 V or other voltage values.The AC voltage may have a frequency of 50 Hz or 60 Hz. The AC voltagecan have amplitudes and frequencies other than those described abovewithout departing from the scope of the present disclosure.

In one embodiment, the voltage source 102 supplies a DC voltage. The DCvoltage can include voltages between 50 V DC 500 V DC. The DC voltagecan have values outside this range without departing from the scope ofthe present disclosure.

The voltage source 102 can include a power outlet from which electricityis provided to power electronic devices and circuits. The power outletcan include common wall outlets in accordance with recognized standardsof various municipalities and regions.

In one embodiment, the electronic device 104 is a light fixture. Thelight fixture can include interior lights of a home or building,exterior lights of the home or building, streetlights, or other types oflight fixtures. In one embodiment, the electronic device 104 can includecomputing devices, home appliances, hospital equipment, or other typesof electronic devices that receive power from a voltage source.

The circuit board 106 controls the supply of power from the voltagesource 102 to the electronic device 104. For example, the electronicdevice 104 may be configured to operate on a voltage other than thevoltage provided by the voltage source 102. Accordingly, one function ofthe circuit board 106 may be to convert the input voltage received fromthe voltage source 102 to an output voltage that can power theelectronic device 104.

The circuit board 106 can receive an AC voltage from the voltage source102 and can convert the AC voltage to a DC voltage. The circuit board106 can receive an AC voltage from the voltage source 102 and cantransform the AC voltage to an AC voltage having a higher or loweramplitude. The circuit board 106 can receive a DC voltage from thevoltage source 102 and can output an AC voltage to the electronic device104. The circuit board 106 can receive a DC voltage and can convert itto a DC voltage having a higher or lower value. Accordingly, the circuitboard 106 is able to receive an input voltage from the voltage source102 and to convert the input voltage to an output voltage of a desiredtype and amplitude.

The circuit board 106 includes an integrated circuit 108 that controlsthe supply of power to the electronic device 104. For example, theoutput voltage can be provided to the electronic device 104 via one ormore power transistors. The gates of the power transistors arecontrolled by the integrated circuit 108. Accordingly, the integratedcircuit 108 controls switching of the power transistors, therebycontrolling the supply of the output voltage to the electronic device104.

The integrated circuit 108 includes a supply voltage terminal 112. Thesupply voltage terminal 112 receives a supply voltage. The supplyvoltage can be a positive DC supply voltage of the integrated circuit108.

The integrated circuit 108 does not enable the supply of the outputvoltage to the electronic device 104 unless the supply voltage ispresent at the supply voltage terminal 112. Accordingly, if the supplyvoltage terminal 112 does not receive the supply voltage, then theintegrated circuit 108 will not enable operation of the electronicdevice 104.

The supply voltage terminal 112 of the integrated circuit 108 is coupledto a capacitor 114. The capacitor 114 is external to the integratedcircuit 112. In one embodiment, the integrated circuit 108 will notenable the output of the output voltage until the capacitor 114 ischarged to the supply voltage value. When the capacitor 114 is chargedto the supply voltage value, the supply voltage terminal 112 receivesthe supply voltage value.

When the voltage source 102 is not connected to the circuit board 106,the integrated circuit 108 is not operational and the capacitor 114 isnot charged to the supply voltage value. The result is that when thevoltage source is first connected to the circuit board 106, theintegrated circuit 108 does not immediately enable supply of the outputvoltage to the electronic device 104. The integrated circuit 108 willnot enable supply of the output voltage to the electronic device 104until the capacitor 114 is charged to the supply voltage value.

The integrated circuit 108 includes a high-voltage startup circuit 110.The high-voltage startup circuit 110 initiates charging of the capacitor114 to the supply voltage value when the circuit board 106 is initiallyconnected to the voltage source 102. In particular, when the voltagesource 102 is first connected to the circuit board 106, the circuitboard 106 receives the input voltage from the voltage source 102. Theintegrated circuit 108 receives, on one of its terminals, a voltageindicating that the circuit board 106 is connected to the voltage source102. The high-voltage startup circuit 110 initiates charging of thecapacitor 114 responsive to the circuit board 106 receiving the inputvoltage from the voltage source 102.

In one embodiment, the high-voltage startup circuit 110 initiatescharging of the capacitor 114 by outputting a first charging current.When the input voltage is received from the voltage source 102, thehigh-voltage startup circuit 110 outputs the first charging current. Thefirst charging current begins the charging of the capacitor 114 to thesupply voltage value.

The first charging current supplied by the high-voltage startup circuit110 may not, by itself, be sufficient to charge the capacitor 114 to thesupply voltage value in a satisfactorily short time range. In theexample in which the electronic device 104 is a light fixture, it may bedesirable that the light fixture illuminates within a selected amount oftime after providing the input voltage from the voltage source 102 tothe circuit board 106. The delay between receipt of the input voltageand the turning on of the light fixture is based, at least in part, onhow quickly the capacitor 114 charges to the supply voltage level of theintegrated circuit 108. If the high-voltage startup circuit 110 is notable to output a charging current of sufficient magnitude to charge thecapacitor 114 within the selected amount of time, then the light fixturewill not illuminate within the selected amount of time.

Accordingly, the circuit board 106 includes a boost circuit 116 thatreduces the charging time of the capacitor 114. The boost circuit 116receives or detects the first charging current provided by thehigh-voltage startup circuit 110 and provides a second charging current.In one embodiment, the second charging current is a current that is anamplification of the first charging current, or an amplification of aportion of the first charging current, provided by the high-voltagestartup circuit 110. Accordingly, the boost circuit 116 amplifies thecharging current provided by the high-voltage startup 110.

The second charging current helps charge the capacitor 114 to the supplyvoltage level. Because the second charging current is an amplificationof the first charging current, the second charging current helps tocharge the capacitor 114 much more quickly than could be accomplished bythe first charging current alone. Accordingly, the boost circuit 116augments the charging of the capacitor 114.

In one embodiment, the boost circuit 114 includes a bipolar transistor.The bipolar transistor includes a base terminal, a collector terminal,and an emitter terminal. The bipolar transistor receives, as a basecurrent, at least a portion of the first charging current. The bipolartransistor outputs a second charging current. The second chargingcurrent is an emitter current or collector current of the bipolartransistor. The emitter current of a bipolar transistor is anamplification of the base current by the transistor current gain factorβ. In one embodiment, at least a portion of the second charging currentserves to charge the capacitor 114. In one embodiment, the entirety ofthe second charging current can charge the capacitor 114.

While FIG. 1 shows a single capacitor 114, in practice there may bemultiple capacitors coupled to the supply voltage terminal 112 of theintegrated circuit 108. For example, a first capacitor may be directlycoupled between the supply voltage terminal and ground. A secondcapacitor may be coupled to the supply voltage terminal via one or moreresistors and/or transistors. The first and second capacitors may becoupled together in such a way that charging one of the capacitors tothe supply voltage value will require charging the other capacitor tothe supply voltage value. Accordingly, the second charging current mayassist in charging both capacitors to the supply voltage level.Alternatively, the second charging current may augment charging of afirst capacitor by enabling the first charging current to primarilycharge the first capacitor while the second charging current charges thesecond capacitor.

The boost circuit 116 can greatly decrease a charging time of thecapacitor 114. The result is that the supply voltage terminal 112reaches the supply voltage level much more quickly than would bepossible in the absence of the boost circuit 116. Accordingly, theintegrated circuit 108 enables supply of the output voltage to theelectronic device 104 much more quickly than would happen in the absenceof the boost circuit 116.

In one embodiment, the circuit board 106 is external to the electronicdevice 104. Thus, while FIG. 1 shows the circuit board 106 as being partof the electronic device 104, in some embodiment the circuit board 106may be external to the electronic device 104. Additionally, the circuitboard 106 can include multiple circuit boards configured to collectivelyoperate the electronic device 104.

FIG. 2 is a schematic diagram of a circuit board 106, according to oneembodiment. The circuit board 106 includes an input terminal 122, anoutput terminal 124, voltage conversion circuitry 120, an integratedcircuit 108, and boost circuit 116. The components of the circuit board106 cooperate to manage supply of electricity to an electronic device104.

The input terminal 122 receives an input voltage V_(i). The inputvoltage V_(i) can be received from a voltage source 102 as described inrelation to FIG. 1. The input voltage V_(i) can include an AC voltage orDC voltage.

The voltage conversion circuitry 120 receives the input voltage V_(i)from the input terminal 122. The voltage conversion circuitry 120converts the voltage V_(i) to an output voltage V_(o) that is providedto the output terminal 124. The output voltage V_(o) powers theelectronic device 104.

The voltage conversion circuitry 120 can include various circuits andcomponents for converting the input voltage V_(i) to the output voltageV_(o). The voltage conversion circuitry 120 can include rectifiers,transformers, inverters, voltage regulators, integrated circuits,transistors, resisters, inductors, diodes, and capacitors.

The voltage conversion circuitry 120 can include one or more powertransistors for supplying the output voltage V_(o) to the outputterminal 124. In one embodiment, the voltage conversion circuitry 120includes a bridge leg including a high side power transistor and a lowside power transistor. The voltage conversion circuitry 120 can includeother configurations of power transistors or other circuitry forcontrolling supply of the output voltage V_(o) without departing fromthe scope of the present disclosure.

The integrated circuit 108 includes a supply voltage terminal VCC, aninput voltage terminal VAC, and a gate drive terminal GD. The supplyvoltage terminal VCC is one example of the supply voltage terminal 112of FIG. 1. The integrated circuit 108 also includes a high-voltagestartup circuit 110. The integrated circuit 108 controls the supply ofpower to the electronic device 104.

The input voltage terminal VAC of the integrated circuit 108 is coupledto the input terminal 122 of the circuit board 106 via a first diode D1and a second diode D2. When the input terminal 122 receives an ACvoltage from the voltage source 102, the diodes D1 and D2 rectify thevoltage. The terminal VAC of the integrated circuit 108 receives therectified voltage from the diodes D1 and D2. Accordingly, the integratedcircuit 108 detects the presence of the input voltage V_(i) by receivingthe rectified voltage at the terminal VAC, in one embodiment.

After startup of the integrated circuit 108, the integrated circuit 108is powered by the supply voltage received at the supply voltage terminalVCC. The value of the supply voltage is between 3 V and 20 V DC. Thesupply voltage can have other values without departing from the scope ofthe present disclosure.

When the circuit board 106 newly receives the input voltage V_(i) at theinput terminal 122, the integrated circuit 108 receives the rectifiedvoltage at VAC. The integrated circuit 108 wakes up responsive toreceiving the rectified voltage at the terminal VAC. The integratedcircuit 108 is powered by the rectified voltage received at the terminalVAC until the supply voltage is present at the supply voltage terminalVCC. The integrated circuit 108 not will enable power to be provided tothe electronic device 104 until the supply voltage is present at thesupply voltage terminal VCC.

Accordingly, upon initially receiving the rectified voltage at theterminal VAC, the integrated circuit 108 enters a startup mode andbegins charging the capacitor 114A to the supply voltage. In particular,the high-voltage startup circuit 110 provides a first charging currentto the supply voltage terminal VCC. The first charging current helps tocharge the capacitor 114A to the supply voltage value. A capacitor 114Bis coupled to the capacitor 114A. The function of the capacitor 114B isdescribed in more detail below with relation to FIG. 3.

The boost circuit 116 augments the charging of the capacitor 114A to thesupply voltage during the startup mode. In particular, the boost circuit116 supplies a second charging current based on the first chargingcurrent. The second charging current augments the charging of thecapacitor 114A. The second charging current can be an amplification ofthe first charging current. The boost circuit 116 includes thetransistor Q1 and the resistor R1. The circuit board also includesresistors R2 and R3, breakdown diode D3, and transistor Q2. The functionof the boost circuit 116 is described in more detail below with relationto FIG. 3.

In one embodiment, the integrated circuit 108 includes a gate driveterminal GD. The terminal GD drives one or more power transistorsincluded in the voltage conversion circuitry 120. The output voltageV_(o) is provided at the output terminal 124 by driving the one or morepower transistors. Accordingly, the integrated circuit 108 controlssupply of the output voltage V_(o) to the electronic device 104 bydriving the gates of the one or more power transistors.

The integrated circuit 108 begins driving the one or more powertransistors after the startup operation is complete. The supply voltagepowers the driving of the power transistors via the terminal GD.Accordingly, power will not be supplied to the electronic device 104until the startup operation is complete and the supply voltage ispresent at the terminal 112.

Although FIG. 2 illustrates a single gate drive terminal GD, in someembodiments the integrated circuit 108 can include multiple gate driveterminals for driving multiple power transistors. In one example thevoltage control circuitry 120 includes a power factor controller. Theintegrated circuit 108 can include one or more gate drive terminals fordriving one or more power transistors of the power factor controller. Inone example, the voltage control circuitry 120 includes a half bridgeincluding an upper MOSFET and a lower MOSFET. The integrated circuit 102can include respective drive terminals for driving the upper MOSFET andthe lower MOSFET. In one example, the voltage control circuitry 120includes both a power factor controller and a half bridge. Theintegrated circuit 108 can include terminals for driving powertransistors of both the power factor controller and the half bridge.

FIG. 2 illustrates the integrated circuit 108 as having terminals VAC,GD, and VCC. However, in practice, the integrated circuit 108 can haveadditional terminals including ground supply terminals, bootstrapterminals, terminals that monitor or control various aspects of thevoltage conversion circuitry 120, and other terminals that can beutilized by an integrated circuit in conjunction with a circuit boardfor providing power to an electronic device. Those of skill in the artwill recognize, in light of the present disclosure, that many othervarious configurations of an integrated circuit and voltage conversioncircuitry can be utilized without departing from the scope of thepresent disclosure.

FIG. 3 is a schematic diagram of a portion of the circuit board 106 ofFIG. 2, according to one embodiment. FIG. 3 illustrates various chargingcurrents that charge the capacitors 114A, 114B to the supply voltagelevel. The charging currents are present during a startup operation ofthe integrated circuit 108.

The circuit board 106 includes a capacitor 114A and a capacitor 114B.The capacitor 114A is coupled between the terminal 112 of the integratedcircuit 108 and ground. The capacitor 114B is coupled between acollector terminal of the transistor Q1 and ground.

In one embodiment, the capacitor 114B has a capacitance that is largerthan the capacitance of the capacitor 114A. The comparatively largecapacitance of the capacitor 114B allows the capacitor 114B to maintaina voltage close to the desired supply voltage value when charge is drawnfrom the capacitor 114A. The presence of the transistor Q2 and theresistors R2 and R3 ensures that the voltage on the capacitor 114A istied to the voltage of the capacitor 114B. The Zener diode D3 sets thevoltage on the base of the transistor Q2, and thus helps set the voltageon the emitter of Q2. In particular, if current flows from the capacitor114A the transistor Q2 becomes forward biased and a current will flowfrom the capacitor 114B to the capacitor 114A via the transistor Q2.Accordingly, charging or discharging of one of the capacitors willresult in the charging or discharging of the other capacitor.

In one example, the capacitance of the capacitor 114A is 10 μF and thecapacitance of the capacitor 114B is 180 μF. Accordingly, the capacitor114B has a capacitance that is significantly larger than the capacitanceof the capacitor 114A. The capacitors 114A and 114B can have othervalues without departing from the scope of the present disclosure.

During the startup operation, the high-voltage startup circuit 110 ofthe integrated circuit 108 provides a first charging current I_(C1). Thefirst charging current I_(C1) is provided to charge the capacitor 114Ato the supply voltage level. The first charging current I_(C1) may havea value between 0.5 mA and 0.2 mA.

Because the capacitor 114B has a significantly higher capacitance thanthe capacitor 114A, the charging rate of the capacitor 114A is limitedby the charging rate of the capacitor 114B. The relatively small firstcharging current I_(C1) is not able, by itself, to rapidly charge boththe capacitors 114A, 114B.

The boost circuit 116 augments the charging of the capacitors 114A,114B. When the first charging current I_(C1) begins to flow, a portionof the first charging current I_(C1) becomes a base current I_(B). Thebase current I_(B) flows into a base terminal of the bipolar transistorQ1. The transistor Q1 passes a second charging current I_(C2) based onthe base current I_(B). The second charging current I_(C2) augments orhastens the charging of the capacitors 114A, 114B.

The emitter current in a bipolar transistor is related to the basecurrent by a current gain factor β. In particular, the emitter currentis given by the relationship:I _(E) =I _(B)*(1+β),Where I_(E) is the emitter current and I_(B) is the base current. Thesecond charging current I_(C2) is the emitter current of the transistorQ1. Thus, the second charging current I_(C2) is equal to the basecurrent I_(B) multiplied by the current gain factor β. Accordingly, thesecond charging current I_(C2) is an amplification of the base currentI_(B) by the gain factor β. Because the base current I_(B) is based onthe first charging current I_(C1), the second charging current I_(C2) isan amplification of the first charging current I_(C1). The value of β istypically between 15 and 200, though other values of β can be usedwithout departing from the scope of the present disclosure. While FIGS.2 and 3 illustrate a boost circuit 116 including the NPN bipolartransistor Q1, other designs of a boost circuit 116 can be used withoutdeparting from the scope of the present disclosure. For example, a boostcircuit 116 could utilize a PNP bipolar transistor, or variousconfigurations of multiple transistors and other circuit components, aswill be apparent to those of skill in the art in light of the presentdisclosure.

A portion of the second charging current I_(C2) charges the capacitor114B. In particular, the current I_(CB) directly charges the capacitor114B. The current I_(CA) directly charges the capacitor 114A.

The current I_(CB) is related to the current I_(CA) by the followingrelationship:I _(CB) =I _(CA)*(C _(B) /C _(A)),where C_(A) is the capacitance the capacitor 114A and C_(B) is thecapacitance of the capacitor 114B.

One effect of the boost circuit is that nearly all of the first chargingcurrent I_(C1) charges the capacitor 114A because I_(B) is relativelysmall compared to I_(C1). The second charging current I_(C2) charges thecapacitor 114B. The comparatively large second charging current I_(C2)charges the comparatively large capacitor 114B. In the absence of theboost circuit 116 and the second charging current I_(C2), the firstcharging current I_(C1) would have to charge both the capacitors 114A,114B, possibly resulting in an unacceptably slow delay between receivingthe input voltage V_(i) and providing the output voltage V_(o). Instead,the boost circuit 116 results in the rapid charging of both capacitors114A, 114B.

In one embodiment, the resistor R1 is coupled between the emitterterminal of the transistor Q1 and a voltage V_(BULK) provided by thevoltage conversion circuitry 120. The presence of R1 can enable thedissipation of a large amount of heat without adding an expensivehigh-power transistor. The value of R1 can be chosen so that almost allthe voltage drop occurs across the resistor R1. The value of R1 can bechosen by the relationshipR1>(V _(BULK) /I _(C1))*(CA/CB).In one example, the resistor R1 has a value of 22 kΩ and V_(BULK) has avalue between 400 V and 500 V. In one example, the resistor R2 has avalue of about 1Ω. In one example, the resistor R3 has a value of about1 kΩ Other values of the resistors R1-R3 can be used without departingfrom the scope of the present disclosure.

In one embodiment, a first terminal of the capacitor 114B is coupled toan auxiliary voltage V_(AUX). The auxiliary voltage V_(AUX) is providedby the voltage conversion circuitry 120. During the startup operation,V_(AUX) is not provided to the capacitor 114B. The auxiliary voltage canbe provided by an auxiliary winding of the voltage conversion circuitry120. During the startup operation, the auxiliary voltage V_(AUX) is notprovided to the capacitor 114B. After the startup operation theauxiliary voltage V_(AUX) is provided to the capacitor 114B. After thestartup operation, the value of the auxiliary voltage is the supplyvoltage value. Accordingly, after the startup operation, the supplyvoltage is provided by the auxiliary winding of the voltage conversioncircuitry 120.

FIG. 4 illustrates a plurality of graphs representing various voltagesand currents related to a startup operation of an integrated circuit,according to one embodiment. In particular, FIG. 4 illustrates a graph140 of a voltage at the VAC terminal of the integrated circuit 108, agraph 142 of a voltage at the supply voltage terminal VCC of theintegrated circuit 108, a graph 144 of a current supplied by thehigh-voltage startup unit 110 of the integrated circuit 108, and a graph146 of a voltage at the terminal GD of the integrated circuit 108. Thevoltages in the graph 140, 142, 146 may not be of the same scale. Forexample, the amplitude of the rectified voltage at VAC may be between 50V and 500 V while the value of the supply voltage may be between 3 V and20 V. Additionally, the frequency of the rectified voltage may bedifferent than shown in FIG. 4.

At time t0, the input voltage V_(i) is not received from the voltagesource 102. At time t1, the input voltage V_(i) is received from thevoltage source 102 at the input terminal 122. The input voltage V_(i) isrectified and provided to the terminal VAC of the integrated circuit108. The graph 140 illustrates the waveform of the rectified voltagereceived at the terminal VAC at time t1. The integrated circuit 108enters a startup mode responsive to receiving the rectified voltage atthe terminal VAC. The rectified voltage powers the integrated circuit108 until the startup operation is complete.

With reference to the graph 142, the voltage at the supply terminal VCCis 0 V between t0 and t1 because the input voltage Vi has not yet beenreceived from the voltage source 102. At t1 the input voltage isreceived and the startup operation begins. The high-voltage startupcircuit 110 begins charging the capacitor 114A by outputting the firstcharging current I_(C1). As the capacitor 114A charges, the voltage atthe supply terminal VCC begins to rise. The voltage at the supplyterminal VCC rises until the voltage reaches a threshold voltage VT attime t2. When the voltage at the terminal VCC reaches the thresholdvoltage VT, the high-voltage startup circuit 110 ceases outputting thefirst charging current I_(C1). The cessation of the first chargingcurrent I_(C1) causes the cessation of the second charging currentI_(C2) because there is no longer a base current I_(B) flowing into thebase of the transistor Q1.

In one example, the startup operation lasts for about 250 ms when theinput voltage V_(i) has a value of 115 V AC. In the absence of the boostcircuit 116, the startup operation for this input voltage V_(i) is about500 ms. At higher input voltages, the benefit of the boost circuit iseven greater. For example, when the input voltage V_(i) is about 300 VAC, the startup operation with the boost circuit 116 is about 150 ms. At300 V AC, the startup operation without the boost circuit 116 is about550 ms. Accordingly, the boost circuit 116 greatly reduces the durationof the startup operation.

After the high-voltage startup circuit 110 has ceased outputting thefirst charging current I_(C1), the voltage of the supply terminal VCCdrops from the threshold voltage VT to the supply voltage value V_(SUP).In one embodiment, the threshold voltage VT is about 17 V. The supplyvoltage value V_(SUP) is about 15 V. Other values can be used for thethreshold voltage and the supply voltage V_(SUP) without departing fromthe scope of the present disclosure. In one embodiment, the startupoperation is complete when the supply voltage terminal VCC reaches thesupply voltage level rather than the threshold voltage VT.

With reference to the graph 144, the first charging current I_(C1) isnot supplied between times t0 and t1. At t1, the high-voltage startupcircuit 110 enters the startup operation and begins supplying the firstcharging current I_(C1). The first charging current I_(C1) is supplieduntil the end of the startup operation at time t2, as is explained inmore detail below. Though not illustrated in FIG. 4, the second chargingcurrent I_(C2) has a similar waveform as the first charging currentI_(C2). The second charging current I_(C2) has a greater magnitude thanthe first charging current I_(C1). The second charging current I_(C2)activates when the first charging current activates. The second chargingcurrent I_(C2) ceases when the first charging current I_(C1) ceases. Inone example, the first charging current I_(C1) has a magnitude of about1 mA. The second charging current I_(C2) has a magnitude of about 20 mA.Other values of the first and second charging current I_(C1) and I_(C2)are possible without departing from the scope of the present disclosure.

With reference to the graph 146, after the startup operation is completeat t2, there is a drive initialization period between t2 and t3. Afterthe drive initialization period is complete at t3, the integratedcircuit 108 begins driving the gates of one or more power transistors,thereby enabling the supply of the output voltage V_(o) the electronicdevice 104. The integrated circuit 108 switches the power transistor onand off by modulating the voltage at the terminal GD. Thus, at T3, theelectronic device receives the output voltage V_(o) begins to function.The integrated circuit 108 enables the supply of V_(o) to the electronicdevice 102 responsive to the supply voltage terminal VCC reaching thesupply voltage value V_(SUP).

FIG. 5 is a flow diagram of a process 500, according to one embodiment.At 502 the process 500 includes receiving an input voltage at an inputterminal of a circuit board. At 504 the process 500 includes outputting,responsive to receiving the input voltage, a first charging current froman integrated circuit positioned on the circuit board. At 506 theprocess 500 includes passing at least a portion of the first chargingcurrent through a base terminal of a bipolar transistor positioned onthe circuit board. At 508 the process 500 includes charging a firstcapacitor to a supply voltage value of the integrated circuit bysupplying a second charging current from the bipolar transistor. At 510the process 500 includes enabling, with the integrated circuit, supplyof an output voltage from the circuit board responsive to the firstcapacitor reaching the supply voltage value.

FIG. 6 is a flow diagram of a process 600, according to one embodiment.At 602, the process 600 includes charging, to a supply voltage value, afirst capacitor coupled to a supply voltage terminal of an integratedcircuit by supplying a first charging current from the integratedcircuit as a startup procedure of the integrated circuit. At 604, theprocess 600 includes augmenting the charging of the first capacitor tothe supply voltage level by generating, with a boost circuit external tothe integrated circuit, a second charging current by amplifying aportion of the first charging current. At 606, the process 600 includesenabling, with the integrated circuit, supply of an output voltage to anelectronic device responsive to the first capacitor reaching the supplyvoltage level.

The various embodiments described above can be combined to providefurther embodiments. All U.S. patent application publications and U.S.patent applications referred to in this specification and/or listed inthe Application Data Sheet are incorporated herein by reference, intheir entirety. Aspects of the embodiments can be modified, ifnecessary, to employ concepts of the various patents, applications andpublications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A device comprising: an input terminal that receives an input voltage; an output terminal that supplies an output voltage; a first capacitor; an integrated circuit that controls supply of the output voltage from the output terminal, the integrated circuit including: a supply voltage terminal that receives a supply voltage of the integrated circuit and is coupled to the first capacitor; and a high voltage startup circuit that begins charging the first capacitor to a supply voltage value by supplying a first charging current from the supply voltage terminal when the input terminal receives the input voltage; a boost circuit external to the integrated circuit and that augments the charging of the first capacitor by generating a second charging current based on the first charging current.
 2. The device of claim 1, wherein the integrated circuit is configured to enable the supply of the output voltage responsive to the supply voltage terminal reaching the supply voltage value.
 3. The device of claim 1, wherein the boost circuit includes a bipolar transistor having a base terminal that receives a portion of the first charging current.
 4. The device of claim 3, wherein the bipolar transistor supplies the second charging current as a collector current or an emitter current of the bipolar transistor.
 5. The device of claim 4, further comprising a second capacitor coupled to the bipolar transistor.
 6. The device of claim 5, wherein the second capacitor has a capacitance at least 10 times greater than a capacitance of the first capacitor.
 7. The device of claim 6, wherein the first and second capacitors are coupled together such that if there is a difference in voltage between the first and second capacitors, a current will flow between the first and second capacitors.
 8. The device of claim 6, wherein the first charging current is supplied to the first capacitor via the supply voltage terminal.
 9. The device of claim 5, wherein the boost circuit augments the charging of the first capacitor by charging the second capacitor.
 10. The device of claim 1, wherein the input voltage is an AC voltage with an amplitude greater than or equal 90 V.
 11. The device of claim 10, wherein the output voltage is a DC voltage between 10 V and 500 V.
 12. A method, comprising: charging, to a supply voltage value, a first capacitor coupled to a supply voltage terminal of an integrated circuit by supplying a first charging current from the integrated circuit as a startup procedure of the integrated circuit; augmenting the charging of the first capacitor to the supply voltage level by generating, with a boost circuit external to the integrated circuit, a second charging current by amplifying a portion of the first charging current; and enabling, with the integrated circuit, supply of an output voltage to an electronic device responsive to the first capacitor reaching the supply voltage level.
 13. The method of claim 12, further comprising: receiving an input voltage at a first terminal of a circuit board; and initiating the startup procedure responsive to receiving the input voltage at the first terminal.
 14. The method of claim 13, further comprising generating the output voltage from the input voltage.
 15. The method of claim 12, further comprising generating the second charging current with a bipolar transistor of the boost circuit.
 16. The method of claim 15, further comprising generating the second charging current by receiving a portion of the first charging current in a base terminal of the bipolar transistor.
 17. The method of claim 16, further comprising augmenting charging of the first capacitor to the supply voltage level by charging a second capacitor to the supply voltage level with the second charging current.
 18. A method, comprising: receiving an input voltage at an input terminal of a circuit board; outputting, responsive to receiving the input voltage, a first charging current from an integrated circuit positioned on the circuit board; passing at least a portion of the first charging current through a base terminal of a bipolar transistor positioned on the circuit board external to the integrated circuit; charging a first capacitor to a supply voltage value of the integrated circuit by supplying a second charging current from the bipolar transistor; and enabling, with the integrated circuit, supply of an output voltage from the circuit board responsive to the first capacitor reaching the supply voltage value.
 19. The method of claim 18, further comprising charging the first capacitor to the supply voltage level by charging a second capacitor to the supply voltage level.
 20. The method of claim 19, wherein enabling supply of the output voltage includes driving a power transistor with the integrated circuit.
 21. A device comprising: an input terminal that receives an input voltage; an output terminal that supplies an output voltage; a first capacitor; an integrated circuit that controls supply of the output voltage from the output terminal, the integrated circuit including: a supply voltage terminal that receives a supply voltage and is coupled to the first capacitor; and a high voltage startup circuit that begins charging the first capacitor to a supply voltage value by supplying a first charging current from the supply voltage terminal when the input terminal receives the input voltage; and a boost circuit that augments the charging of the first capacitor by generating a second charging current based on the first charging current, the boost circuit includes: a bipolar transistor having a base terminal that receives a portion of the first charging current.
 22. The device of claim 21, wherein the bipolar transistor supplies the second charging current as a collector current or an emitter current of the bipolar transistor. 